Woofer sound without enclosure

gchrist · 10th November 2003, 05:10 AM

I am currently building the reference monitor loudspeaker with scan speak drives. I tested the crossover with the drivers connected before installing them in the wooden enclosure. The sound produced was very "thin" with very little low frequencies and very "cold". The same sound occured with or without the crossover connected to the woofers. I tried another woofer I had in hand (an old KEF Bextrene woofer) and this one played much better. Note that the bextrene woofer was designed for a closed enclosure without a bass reflex port. The reference monitor is a bass reflex port.
So the question are:

1)Will the sound of my scan speak drives change so much when I will put them in the enclosure? Does the enclosure magnify the low frequencies so much?

2) I have used an enclosure with thicker panels. Does this mean that I have to adjust the port hole lenght? If yes then how?

Thank you
George
Athens

SkinnyBoy · 10th November 2003, 05:14 AM

yes.. the enclosure will make it sound how it should... I have no idea what your second question is.. lol

Wright · 10th November 2003, 06:02 AM

I think he is saying that he used thicker cabinet walls then the plans called for. Assuming his internal volume was the same, if he surface mounts the port, the inside tube will be 3/4" farther out of the cabinet then before. Not sure what effect that will have though, maybe slightly increasing the cabinet volume including the slug of air in the port?

gchrist · 10th November 2003, 06:03 AM

SkinnyBoy thank you for your reply.

About my second question:

The initial box enclosure is made out of 25mm thick side and back panels. I have used panels that are a bit more thick (32mm). The port lenght is 14.5 cm long in the initial design with 25 mm thick panels. Now that I have 32 mm thick panels do I have to change the lenght of the port from 14.5 to something else?

Thank you
George

daatkins · 10th November 2003, 07:23 AM

George,
You do not need to change the port length if you maintained the same internal volume of air when you increased the wall thickness.

If you kept the same external diamensions when increasing wall thickness then the amount of air in the box will be less so it might be necessary to retune the port. To recalculate the new port length, you need to specifiy the original box volume and tuning frequency as well as the Qts of the woofer.

Nice one,
David.

gchrist · 10th November 2003, 07:32 AM

I have retained the same internal volume so no changes will be made.

Thank you all!

George

10th November 2003, 05:10 AM	#1
gchrist diyAudio Member Join Date: Mar 2002 Location: Athens Greece	Woofer sound without enclosure I am currently building the reference monitor loudspeaker with scan speak drives. I tested the crossover with the drivers connected before installing them in the wooden enclosure. The sound produced was very "thin" with very little low frequencies and very "cold". The same sound occured with or without the crossover connected to the woofers. I tried another woofer I had in hand (an old KEF Bextrene woofer) and this one played much better. Note that the bextrene woofer was designed for a closed enclosure without a bass reflex port. The reference monitor is a bass reflex port. So the question are: 1)Will the sound of my scan speak drives change so much when I will put them in the enclosure? Does the enclosure magnify the low frequencies so much? 2) I have used an enclosure with thicker panels. Does this mean that I have to adjust the port hole lenght? If yes then how? Thank you George Athens

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10th November 2003, 05:14 AM	#2
SkinnyBoy Banned Join Date: Nov 2002 Location: Adelaide, Australia	yes.. the enclosure will make it sound how it should... I have no idea what your second question is.. lol

10th November 2003, 06:02 AM	#3
Wright diyAudio Member Join Date: Apr 2003 Location: Seattle, WA	I think he is saying that he used thicker cabinet walls then the plans called for. Assuming his internal volume was the same, if he surface mounts the port, the inside tube will be 3/4" farther out of the cabinet then before. Not sure what effect that will have though, maybe slightly increasing the cabinet volume including the slug of air in the port?

10th November 2003, 06:03 AM	#4
gchrist diyAudio Member Join Date: Mar 2002 Location: Athens Greece	SkinnyBoy thank you for your reply. About my second question: The initial box enclosure is made out of 25mm thick side and back panels. I have used panels that are a bit more thick (32mm). The port lenght is 14.5 cm long in the initial design with 25 mm thick panels. Now that I have 32 mm thick panels do I have to change the lenght of the port from 14.5 to something else? Thank you George

10th November 2003, 07:23 AM	#5
daatkins diyAudio Member Join Date: Aug 2001 Location: Bath, UK	George, You do not need to change the port length if you maintained the same internal volume of air when you increased the wall thickness. If you kept the same external diamensions when increasing wall thickness then the amount of air in the box will be less so it might be necessary to retune the port. To recalculate the new port length, you need to specifiy the original box volume and tuning frequency as well as the Qts of the woofer. Nice one, David.

10th November 2003, 07:32 AM	#6
gchrist diyAudio Member Join Date: Mar 2002 Location: Athens Greece	I have retained the same internal volume so no changes will be made. Thank you all! George

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